After removing the virus that is hiding the folders go to C:\Windows and if you don’t see the Software Distribution folder go to  Folder Options in control panel , under the View tab select “Show hidden files and folders” and press Ok. Right click Software Distribution folder, go to properties, uncheck Hidden, click Apply and then Ok.

If the Software Distribution folder is not hidden check the subfolders and be sure that they are not hidden.

You can also try the fixes from Microsoft website http://support.microsoft.com/kb/910338